Dual temperature- and pH-responsive fluorescence molecular probe for cellular imaging utilizing a PNIPAAm-fluorescein copolymer.

The thermally controlling fluorescence intensity of a molecular probe for cellular imaging has been investigated. A reversible temperature-induced phase transition of N-isopropylacrylamide/fluorescein copolymers [poly(NIPAAm-co-FL)] was used as a molecular switch to control the fluorescence intensity of the imaging probe. The copolymer displayed environmentally sensitive fluorescence properties, in which the fluorescence intensity changed with the response to both the temperature and the pH. Utilizing these features, we monitored the thermal-aggregation process of BSA by the fluorescence resonance energy transfer (FRET) method. Additionally, the cellular uptake in RAW264.7 cells of poly(NIPAAm-co-FL) conjugated with lipid was studied using a confocal laser scanning microscope.